Production of lubricating oils blending stocks

ABSTRACT

The production of normal and premium lube grade blending stocks of 100, 300 and 700 second neutral material along with high boiling by-product material is improved by using a low pressure vacuum tower provided with an overflash separation in the tower bottom from resid.

United States Patent Button et al.

[ 1 Dec. 30, 1975 PRODUCTION OF LUBRICATING OILS I BLENDING STOCKSInventors: Harold O. Button, Yardley, Pa.; Robert A. Trimble, Pitman, N.J.

Assignee: Mobil Oil Corporation, New York,

Filed: July 31, 1974 Appl. No.: 493,306

US. Cl. 208/309; 208/18; 208/349;

208/357 Int. Cl. C10G 41/00 Field of Search 208/18", 309, 349, 357

References Cited UNITED STATES PATENTS Donaldson et al.... 208/183,488,283 1/1970 Button et al. 208/18 Primary ExaminerHerbert LevineAttorney, Agent, or Firm-Charles A. Huggett; Carl D. Farnsworth [57]ABSTRACT The production of normal and premium lube grade blending stocksof I00, 300 and 700 second neutral material along with high boilingby-product material is improved by using a low pressure vacuum towerprovided with an'ove'rflash separation in the tower bottom from resid.

9 Claims, 1 Drawing Figure IOO Normal 100 Premium 300 Normol 300 Premium700 Normal- 700 Premium PRODUCTION OF LUBRICATING OILS BLENDING STOCKSBACKGROUND OF THE INVENTION Lubricating oils of normal and premiumgrades have been developed over the years for many differentapplications of severity use including automotive, transformer oils,turbine oils, and heavy cylinder oils. Whatever the use intended, alubricating oil must be stable,

have a high flash point and retain its lubricating properties over anextended operating period. Separation of the crude into base stocks ofdifferent viscosities is usually carried out by vacuum distillationfollowed by separate treatment of each fraction by solvent extractionand sometimes hydrofinishing in specific applications. The facilitiesrelied upon for processing available crudes are dependent upon thequality of the crude processed and the characteristics of the productdesired. These considerations have grown in importance it is importantto provide a process which will-reduce the quantity of crude processedwithout reducing the quality of product produced. The present inventionis directed to such an improved process.

SUMMARY OF THE INVENTION This invention relates to the preparation oflubricating oils. In a more particular aspect the present invention isconcerned with an improved combination of processing steps for preparingmore select lubricating oil blending stocks. More particularly thepresent invention relates to an improved vacuum tower operation for theseparation of more select fractions of lube oil blending components andcomponents for asphalt production. In a particular aspect the presentinvention is directed to the recovery of 100, 300 and 700 second neutralfractions of a selected boiling range which are more amenable to solventextraction processes and hydrofinishing thereof under conditionsparticularly restricting the volume of oil charge required to produc agiven volume of desired lube oil blending stocks.

DISCUSSION OF SPECIFIC EMBODIMENTS In the combination operation of thepresent invention comprising vacuum distillation, furfural extraction,methyl ethyl ketone-aromatic extraction and hydrofinishing, it has beenfound particularly advantageous to rely upon a low pressure drop vacuumdistillation tower operation designed to operate at a bottom pressure nohigher than mmHg and preferably it is retained at a bottom pressure ofabout 40 mmHg or lower. More particularly, to improve upon the qualityof asphalt producing components, the vacuum tower of the presentinvention withdraws an overflash fraction from the lower portion of thetower higher boiling than a recovered 700 second neutral fraction, whichis passed to a PDA extraction zone with a portion of the remainingvacuum tower bottom residue.

By practicing the processing concepts of the present invention it hasbeen determined that the capital investment of the combination islowered by as much as 10 percent; the utility consumption is lowered byas much as 30 percent; the crude requirements of the process are loweredby as much as 15 percent; the quality of the lube product is improvedand more high melting point paraffin wax is obtained by the process.

In the combination operation of this invention the vacuum tower reliedupon to separate for example Middle East crude into desired lube oilbase stocks is maintained at a bottom pressure lower than normallyemployed heretofore in a packed tower design providing not more thanabout 15 mmHg pressure drop. The vacuum tower is maintained underconditions providing a flash zone temperature within the range of 690 to735F. and a top temperature within the range of to F. The low pressuredrop tower design of this invention permits the more select recovery of100, 300 and 700 second neutral fractions or other fractional variationsthereon such as a two mode operation comprising a 250 second neutral ora 450 second neutral fraction along with an overflash fraction asidentified in the table below.

The vacuum tower design of the present invention is thus novel indesign; a low operating pressure in conjunction with low pressure droppreferably less than 15 mmHg obtained preferably by use of essentially apacked column containing very few, if any, distillation plates. Thevacuum tower design and method of operation is unique in that it permitsthe recovery of more select and narrow boiling range fractions processedto the blending stocks desired through solvent extraction andhydrofinishing.

The lube oil fractions of Table l recovered from the vacuum tower asherein described are then subjected to a sequential treatment offurfural extraction and MEK extraction. Polycyclic materials areundesirable in lubricating oils because of their low viscosity indexesand poor stability. The polycyclic aromatics are removed in thecombination of this invention by furfural extraction. The furfuralextraction operation shown in block flow arrangement consists offacilities or tower arrangements suitable to contact the oil charge withthe selective solvent plus facilities to separate the solvent fromextract and raffinate streams. In this operation, the solvent isvaporized and the heat requirements for this purpose are normally high.Therefore any savings which can be obtained in this high cost areagreatly contributes to the efficieney of the operation. In the specificoperation of the present invention processing more select boiling rangefractions of 100, 300 and 700 second neutral fractions, the extractionoperating conditions can be refined to a point that considerable savingsare realized not only in the quantity of material processed but also inthe volumes of solvent required and the'heat requirements of theoperation. Thus processing the more select and restricted boiling rangematerials recovered as hereinbefore described avoids solventovertreating the low boiling component portion of the particularfraction as well as an insufficient solvent treatment of the highboiling components of the fraction. The savings also contributesignificantly to equipment savings'as mentioned herein. I

More specifically the furfural extraction of the 100 second neutralfraction may be accomplished with 175 percent volume furfural based oncharge at an effective temperature of about 195F. when maintaining thefurfural extraction tower gradient, top/bottom of about 2203/1 80F.

The 300 second neutral fraction may befurfural extracted with 200percent volumesolvent based. on chargeat an effective temperature ofabout 205F. and

.methyl ether ketone-aromatic solvent. The ketone solvent causes wax tosolidify into a filterable crystalline form. The aromatic component ofthe solvent increases the oil dissolving capacity of the solvent. In theMEK (methyl ethyl ketone) extraction operation, the wax bearing oilcharge is mixed with the solvent and the mixture is chilled tocrystallize the waxaThe chilled feed is continuously filtered to recovera wax cake. The MEK dewaxing operation is accomplished at a few degreesbelow in the range of to 20 below the pour point of the product oildesired. Thus a filtrate comprising oil and solvent is recovered whichis then separated to recover a dewaxed oil fraction from the solventmaterial.

In the combination operation of this invention a 50/50 MEK/toluenesolvent composition is generally relied upon to accomplish dewaxing ofthe specific lube oil fractions. This may be varied either way by about25 'v'olppercent. The filtration temperature for the 100 second neutralis about 20F.; for the 300 second neutral about -1 5F; and about 5F. forthe 700 second neutralmaterial. The amount of solvent employed in thevarious steps of MEK solvent dewaxing will vary 'with each fraction butwill be kept to a minimum consistent with obtaining desired results.

The overflash fraction recovered from the lower portion of the vacuumtower is combined with a portion of thevacuum' resid and passed topropane deasphalting. In a specific example it is contemplatedcombinin"g,base on crude charge, about'4 volume percent of the overflashwith a portion of the vacuum resid varying from about to 60 volumepercent as feed to a PDA (propane deasphalting unit). Bright stockviscosities may be varied by varying the amount of resid passed to thePDA unit. In the PDA unit the above defined mixture is treated withpropane solvent near its critical temperature which dissolves thehydrocarbon phase and'rejects the asphaltic materials. In thecombination of this invention, this separation is enhanced by therecovery of overflash material which is combined with a desired portionof the resid withdrawn from the bottom of the vacuum tower. In the rangeof conditions used in the PDA operation such as 100 to 150F. in thebottom and from 150F. to 180F. at the top of the tower, raising thetemperature of the propane reduces its dissolving capacity but improvesits selectivity. On the other hand, increasing the propane to oil ratiofurther increases the separation sharpness. The operating pressure issufficient to retain the propane in liquid phase. The heavy oil productof PDA treatment is thereafter subjected to furfural and MEK treatmentunder conditions particularly selected to retain the oil product insubstantially maximum yields.

The drawingis a schematic arrangement in block flow representing theprocessing combination of the present invention. In the arrangement ofthe drawing, a crude oilcharge is introduced by conduit 2 to a vacuumdistillation column 4 maintained at a bottom pressure of about 40mmI-Ig. The tower 4 is primarily a packed volumn arranged for about 15mmHg pressure drop. The vacuum tower is operated under conditionsselected to produce the fractions identified in Table 1 above along witha gas oil fraction withdrawn from an upper portion of the tower byconduit 6 and a resid material withdrawn from the bottom of the tower byconduit 8. Ina specific operation, the gas oil fraction amounts to about10 vol.% of the charge and the resid is about I 1.5 vol.% of the charge.A 100 second neutral fraction is withdrawn by conduit 10 and amounts toabout 8.6 vol.% of the charge. Any excess of this material over thatdesired to be processed may be withdrawn by conduit 12. A 300 secondneutral oil fraction amounting to about 7.5 vol.% of the charge is withdrawn by conduit 14 and separated into stream 16 for use in preparingnormal oil blending stockand stream 18 for use in preparing premium oilblending stocks. An overflash boiling range material identified in Tablel and amounting to about 4.0 volume of the feed is withdrawn from alower portion of the vacuum tower above the charge inlet by conduit 26.A portion of the vacuum tower resid withdrawn by conduit 8 is withdrawnby conduit 28 and combined with overflash material in conduit 26 beforepassage by conduit 30 to a PDA unit 32. In the PDA unit, the blend ofoverflash with resid and operating conditions relied upon are such as toprovide an oil product comprising about 48.8 vol.% of the charge theretowhich oil product is withdrawn therefrom by conduit 34. An asphaltproduct of the precess is withdrawn by conduit 36. The heavy oil productin conduit 34 is thereafter subjected to furfural extraction conditionsfor the removal of polycyclic material thereby providing a producttherefrom.

amountingto approximately 68 vol.% of the oil stream charged thereto.The raffinate-oil product of extraction is then passed by conduit 38 tosolvent dewaxing accomplished with a MEK/toluene solvent mixture. Inthis operation the conditions are selected to recover about77 vol.% ofthe feed as a dewaxed oily product. The dewaxed oil is then passed byconduit 40 to a hydrofmishing operation wherein it is contacted with ahydrofinishing catalyst at a temperature within the range of 400 to700F. (prefer 450F. to about 550F.) and apressure selected from withinthe range of 200 to 600 psig. In a specific operation a 95V! heavy lubeoil bright stock in conduit 40 is hydrofinished to a color lighter than5 ASTM. This product material will normally boil above about 900F. andis withdrawn by conduit 42.

The 700 second neutral oil fraction in conduits 22 and 24 are passed tofurfural extraction for the removal of polycyclic materials underconditions permitting the recovery of about 55 vol.% of the oil chargein conduit 22 by conduit 44 and about 45 vol.% of the oil charge inconduit 24 by conduit 46. The raffinate phase of furfural extractionrecovered by conduits 44 and 46 are then passed to solvent dewaxing withMEK as herein described. In the solvent dewaxing operation theconditions are selected to permit the recovery of an oil productamounting to about 77 vol.% of the charge in conduit 44 by conduit 48and about 6 6 vol.% the charge in conduit 46 bycon duit 50. The oilproduct in conduit 48 prepared from 700 second neutral material will beabout a normal 97 VI dewaxed material. This material produced for use asnormal blending stock may be subjected to hydrofinishing conditions ifdesired. The premium oil blending stock recovered by conduit 50 issubjected to hydrofinishing temperature conditions and catalyst contactselected to improve the quality of this material suitable for use aspremium blending stock. In this specific arrangement a 100 VI dewaxedmaterial is produced and will be withdrawn from the hydrofinishingoperation by conduit 52. The 300 second neutral material recovered fromvacuum distillation is passed by conduit 16 and 18 to furfuralextraction operation particularly designed to produce a normal oilproduct recovered by conduit 54 and a premium oil product recovered byconduit 56. The normal oil furfural raffinate amounts to about 55 vol.%of the oil charge and the premium oil raffinate amounts to about 45vol.% of the oil charged. The raffinate streams in conduits 54 and 56are then subjected to solvent dewaxing by MEK to produce dewaxed oilproduct recovered by conduit 58 and premium oil by conduit 60. Thenormal oil in conduit 58 may be hydrofmished if desired. This materialwill be about a 104 VI dewaxed material. The premium oil raffinate inconduit 60 is subjected to hydrofinishing conditions to remove aromaticsand produce a stable turbine oil product. The hydrofinished premium oilis recovered by conduit 62 as a 108 VI dewaxed material (300 secondneutral) for blending purposes. The 100 second neutral oil fractionrecovered from the vacuum tower by conduit is subjected to furfuralextraction. A raffinate fraction amounting to about 54 vol.% of the 100neutral charge is recovered by conduit 64 and separated into two streams66 and 68. Each of the oil streams in conduits 66 and 68 are subjectedto solvent dewaxing by MEK. In this operation about 78 vol.% of the oilcharge in conduit 66 is recovered as a dewaxed oil in conduit 70 andabout 83 vol.% of the charge in conduit 68 is recovered as a dewaxedpremium oil blending component by conduit 72. The dewaxed (100 neutral)oil product recovered by conduit 70 is about a 106 VI material. Thepremium oil in conduit 72 is subject to hydrofinishing conditions tostabilize the oil before it is recovered by conduit 74 as a 110 VIdewaxed material.

In the combination operation herein described, a combined extract phaseis recovered as by conduit 76 and a combined wax phase is recovered bymeans represented by conduit 78. To simplify understanding of thecomplex processing arrangement of the present invention relying uponknown processing technology,

the various furfural extraction steps, MEK solvent de- 6 productblending stock. For example, when charging 15469 (BCD) barrels percalender day, of reduced crude to the improved vacuum tower design andoperation of this invention, the following product distribu- Animportant auxiliary benefit of practicing the processing concepts of thepresent invention is the production of more select components forasphalt production. More particularly, a full range of paving andindustrial asphalts can be formulated from lube byproducts by eitherdirect blending and blending followed by oxidation. In a particularaspect, asphalt penetration grades 65, and 200 have been formulated fromblends of some or all of the following lube streams (consult block flowdrawing) vacuum tower resid (stream 8), vacuum tower overflash (stream26), PD asphalt (stream 36), and furfural extracts (stream 76).

The ability to formulate asphalt from lube byproducts is a valuableadjunct to the present invention for the following reasons: (1) the costof transporting, storing and processing special asphaltic crude on ablocked out refining operation is eliminated, (2) the lube byproductsare upgraded from fuel oil to asphalt value, (3) the downgrading of 300to 500F. kerosine which must be blended with several of these highviscosity lube byproduct streams to meet fuel oil specifications iseliminated.

By selective blending alone or selective blending followed by oxidationof these byproduct streams, asphalts of highly superior quality can beproduced. For example, a 90 penetration grade asphalt may be prepared bya selective blending plus oxidation of vacuum tower resid, vacuum toweroverflash, and PD asphalt to provide the following properties:

Viscosity, CS at 158F. 485 Penetration (77/l00/5) 86 Vis-Pen 41 .700Softening Point, F. 1 l3 Rotating Thin Film Oxidation Ductility at 59F.85 N16" Thin Film Oxidation Ductility at 77F.

Having thus generally described the invention and discussed specificembodiments going to the very essence thereof, it is to be understoodthat no undue restrictions are to be imposed by reason thereof except asdefined by the following claims.

What is claimed is:

1. In an operation for the production of a plurality of different lubestocks from a reduced crude and the recovery of higher boilingby-product material, the improvement which comprises processing areduced crude through a low pressure drop vacuum tower maintained at apressure below 50 mmHg arranged to separate a plurality of differentrelatively narrow boiling range lube base fractions from an overflashfraction boiling in an initial portion above 1000F and a vacuum residfraction, processing each of said relatively narrow boiling rangefractions through a plurality of solvent extraction steps to removeundesired aromatics and wax sufficient to produce normal and premiumgrade lube blending fractions, processing said overflash fractionadmixed with a portion of said resid fractions through propanedeasphalting to produce a raffmate phase and an asphalt phase andprcessing the raffinate phase through solvent extraction to produce animproved bright stock.

2. The operation of claim 1 wherein the lube base fractions are passedsequentially through furfural and methylethyl-ketone solvent extractionsteps.

3. The operation of claim 2 wherein the different lube base fractionsare separated to make a quantity of premium grade lube blendingmaterials and at least the premium grade materials are subjected tohydrofinishmg.

4. The operation of claim 1 wherein the recovery of wax and bright stockis improved and the volume of 8 reduced crude charged to the process issignificantly reduced to produce a desired volume of products.

5. The operation of claim 1 wherein the vacuum distillation tower isarranged and operated to produce a second neutral fraction and at leastone other fraction boiling intermediate said 100 neutral fraction andsaid overflash fraction.

6. The operation of claim 1 wherein the vacuum furfural andmethyl-ethyl-ketone solvent extraction.

1. IN AN OPERATION FOR THE PRODUCTION OF A PLURALITY OF DIFFERENT LUBESTOCKS FROM A REDUCED CRUDE AND THE RECOVERY OF HIGHER BOILINGBY-PRODUCT MATERIAL, THE IMPROVEMENT WHICH COMPRISES PROCESSING AREDUCED CRUDE THROUGH A LOW PRESSURE DROP VACUUM TOWER MAINTAINED AT APRESSURE BELOW 50 MMHG ARRANGED TO SEPARATE A PLURALITY OF DIFFERENTRELATIVELY NARROW BOILING RANGE LUBE BASE FRACTIONS FROM AN OVERFLASHFRACTION BOILING IS AN INITIAL PORTION ABOVE 1000*F AND A VACUUM RESIDFRACTION, PROCESSING EACH OF SAID RELATIVELY NARROW BOILING RANGEFRACTIONS THROUGH A PLURALITY OF SOLVENT EXTRACTION STEPS TO REMOVEUNDESIRED AROMATICS AND WAX SUFFICIENT TO PRODUCE NORMAL AND PREMIUMGRADE LUBE BLENDING FRACTIONS, PROCESSING SAID OVERFLASH FRACTIONADMIXED WITH A PORTION OF SAID RESID FRACTIONS THROUGH PROPANEDEASPHALTING TO PRODUCE A RAFFINATE PHASE AND AN ASPHALT PHASE ANDPRCESSING THE RAFFINATE PHASE THROUGH SOLVENT EXTRACTION TO PRODUCE ANIMPROVED BRIGHT STOCK.
 2. The operation of claim 1 wherein the lube basefractions are passed sequentially through furfural andmethylethyl-ketone solvent extraction steps.
 3. The operation of claim 2wherein the different lube base fractions are separated to make aquantity of premium grade lube blending materials and at least thepremium grade materials are subjected to hydrofinishing.
 4. Theoperation of claim 1 wherein the recovery of wax and bright stock isimproved and the volume of reduced crude charged to the process issignificantly reduced to produce a desired volume of products.
 5. Theoperation of claim 1 wherein the vacuum distillation tower is arrangedand operated to produce a 100 second neutral fraction and at least oneother fraction boiling intermediate said 100 neutral fraction and saidoverflash fraction.
 6. The operation of claim 1 wherein the vacuumdistillation tower is arranged and operated to produce a 100 secondneutral fraction, a 250 second neutral fraction and another fractionlower boiling than said overflash material.
 7. The operation of claim 1wherein the vacuum distillation tower is operated at a pressure notexceeding about 40 mmHg and the pressure drop therein is less than about15 mmHg.
 8. The operation of claim 1 wherein the vacuum tower isessentially a packed distillation tower.
 9. The operation of claim 1wherein the raffinate product of propane deasphalting is hydrofinisHedafter furfural and methyl-ethyl-ketone solvent extraction.